In tunable radio frequency circuits (RF circuits), it is desirable to have adjustable impedances. The basic two types of adjustable impedances are inductors and capacitors. In some cases, it is desirable to have capacitors which are suited for handling large signals. This type of tunable capacitors can, for example, be used for antenna radio frequency matching, power amplifier output matching and all kinds of radio frequency filters that can face strong signals. Additionally, high-quality factors are desired in some cases, for example to maintain sharp filter curves and a low insertion loss. Moreover, in some applications, high linearity is desirable. For example, for next generation mobile phone systems, very high linearity requirements may become mandatory.
In view of this situation, there is a desire to have a tunable capacitance which comprises a good trade-off between power handling capability, quality factor and linearity.